(CNN) -- Bayern Munich's poor start to the Bundesliga season continued as they were beaten 2-1 at Mainz on Saturday, leaving coach Louis van Gaal still searching for his first win since taking over in the summer.

Mainz celebrate their opening goal in their surprise 2-1 victory over Bayern Munich on Saturday.

Andreas Ivanschitz put Mainz ahead in the 25th minute before Aristide Bance doubled the lead in the 37th. Bayern improved in the second half and got back into the game through an own goal from Nikolce Noveski but, despite their efforts, they were unable to find an equalizer, leaving them in the bottom half of the table with just two points from three matches.

Mainz went ahead in the 25th minute with Ivanschitz scoring his first goal in German football, although Bayern goalkeeper Michael Rensing must accept some of the blame.

The Austrian's low shot towards the bottom corner was within Rensing's reach, but he only got a very weak hand to it and helped the ball into the back of the net.

Bance then scored his second goal in as many games -- beating Daniel van Buyten in the air to head Florian Heller's right-wing cross past Rensing from eight yards out.

Bayern reduced the arrears in the 47th minute when Noveski headed substitute Thomas Muller's cross into his own goal, but the home side held on.